Topic in Focus
How are Infectious Diseases Studied and Treated?
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A novel pathogen is sort of a “black box” for scientists. Initially, little is known about how the pathogen spreads and what health consequences an infection may have for humans. Substantial research and development investment is needed to develop tests, vaccines, and drugs to contain pandemics and treat diseases. Despite all scientific advances in medicine, it is not always possible to develop a vaccine for every new infectious disease.
What is the procedure in diagnostics?
Any person who has become infected with a virus or bacterium must be isolated quickly to prevent further infections and to interrupt infection chains. Sometimes it is difficult to assign the symptoms precisely. The bubonic plague symptoms are initially similar to flu-like symptoms, while those of pneumonic plague are similar to severe pneumonia. Only a medical test can provide an exact diagnosis.
The challenge with new types of pathogens is that there are no tests in the beginning. Researchers must first analyze the pathogen, learn about its properties, and develop tests based on this knowledge. It took two years to discover the pathogen in HIV/AIDS after the disease was first described on 5 June, 1981, by the U.S. Centers for Disease Control and Prevention in Los Angeles (May 1983) and another two to three years until the first reliable tests were available.
“In general, tests are a very important measure to get a pandemic under control. And with Corona in particular, a rapid test showing within 15 to 20 minutes whether a person is infected would be very, very valuable. Then it would be possible to isolate any infected person in a much more targeted manner and thus interrupt infection chains. In the case of HIV, of course, a test does not necessarily make sense in terms of interrupting the chains of infection because it is not transmitted via air. But if I know that I am infected, I can take appropriate safe sex precautions. On the other hand, it is very important to test people for HIV so that I know that I am infected and can get the appropriate medication, because otherwise AIDS will develop. With different diseases come various reasons for testing. But again, the primary goal with Corona is, in my opinion, to find out very quickly who is infected and send them into quarantine.”
“In the beginning, it has been noticed in homosexual men in the USA, who suddenly got this strange, serious disease. Then it was noticed: Even hemophiliacs who have received blood products can be infected. Then it was very quickly concluded that this was an infection. And I really have to say that the Centers for Disease Control in the USA had all the transmission paths figured out within a very short period of time. And that's how they were able to issue at least some initial warnings. Of course, it took another 20 years before drugs were available, which turned this death sentence into a treatable disease. But at least it was possible to say after about a year that the transmission paths are A, B, C, D and here is how you can protect yourself against it.”
With a test, the human organism – for example, in the mucous membranes or the blood – is searched for cues to the pathogen or specific antibodies that the immune system forms against viruses or bacteria. If the result is positive and the person is infected, he or she must remain in isolation until being healthy again, unless the pathogen remains in the body permanently, as is the case with HIV. In addition, people with whom the infected person has had contact must be informed, tested, and isolated if necessary and feasible.
Maintain social distance – hope for a vaccine
To contain the further spread of a virus, specific rules of conduct apply during a pandemic. If the pathogen is spread via the respiratory tract, people should keep their distance. In some cases, events are canceled, and facilities such as childcare centers and schools are closed. This is intended to mitigate the dynamics of the pandemic. In most cases, there are still no specific drugs or vaccines against a new virus.
Vaccinations are the most important measures to protect yourself from an infectious disease. They work on two levels: Since they reduce the further spread of the pathogens, they protect both the vaccinated person (individual protection) and society as a whole (community or herd protection). Infectious diseases such as measles, diphtheria, poliomyelitis (polio) were still widespread decades ago but could be contained by vaccination programs. Smallpox was successfully combated for years through worldwide vaccination programs. According to the WHO, the disease has been considered eradicated since 1979.
Lengthy development period, high costs
The task of research is to develop a vaccine as quickly as possible when a new pathogen breaks out. The clinical development until approval can take up to 15 years and costs billions of euros. Therefore, research and development are carried out both in publicly funded institutions and by the pharmaceutical industry. Before a vaccine is approved, it must pass three time- and cost-intensive phases where research proves its safety and efficacy.
“For many of these new vaccines, the first priority is to demonstrate safety and tolerability. You have to remember that a vaccine is used to treat healthy people, so it has to be very safe first and foremost. And then you have to show that it also protects. That is, from infection and from the disease it triggers. Third, and this is the crucial point, you have to know how long such protection will last. Of course, this can only be observed over a long period of time, a year or more. That means you have to vaccinate and then wait and see how immunity develops in real life, so to speak.”
“Whatever worked for one virus does not necessarily work for the other. We are simply dependent on clinical tests, which will tell us if it is possible to develop effective long-term vaccination protection against this virus. If I may use the example of influenza, which is also a variable virus. Here vaccines have to be adapted once a year, so you have to make a new vaccine every year and re-vaccinate. That is technically possible and is being done today. That is just one example showing that long-term immunity cannot always be achieved.”
After the laboratory development period, only a few people are initially tested during the first phase of a clinical trial. The main objective is to determine whether the vaccine is free of harmful side effects. Up to a thousand test persons are already involved in phase two. Here, the required dosage and protective effects are tested additionally. In the third phase, specific vaccination regimens are verified, and it is examined whether age- or gender-specific differences exist.
Live-attenuated or inactivated vaccines are used for measles and influenza. The virus is thereby injected in either attenuated or inactivated form. These substances train the immune system to fend off the pathogens successfully. Scientists are now also working on new types of vaccines that activate the immune system in different ways to combat pathogens.
It is not always possible to develop a vaccine. For example, there are no vaccines against HIV and malaria, although science and industry have been searching intensely for them worldwide and invested large amounts of money. Sometimes diseases can be controlled quite well without a vaccine. There are preventive drugs against malaria. There are also various drugs against HIV, which help infected people to live a long life. Some of these drugs are also used to protect against infection.
“There is no vaccine against HIV because the virus is highly variable. Our own studies have shown that an infected person carries a swarm of viruses that already differ by 10 percent shortly after infection. That means, if you want to develop a vaccine, you are shooting at a moving target, which is the first difficulty. And the second is that this infection is typically transmitted via the mucous membrane, and here you obviously need different defense barriers than with other infections that pass via the throat, for example. Developing a vaccine that provides proper long-term protection has not been possible to date. It has been possible to create a certain immunity in the short term though. But in case of an infection that lasts a lifetime, where you can also get infected throughout your life, we must of course have long-term immunity. And that simply could not be achieved.”
Vaccines or drugs to be administered in Germany require national approval or approval from the European Commission. Only then is any drug or vaccine available to the entire population. The Paul Ehrlich Institute (PEI) is responsible for the approval of biological drugs and vaccines in Germany. It monitors their quality, efficacy, and safety. At the PEI there is also a WHO Collaborating Center for the standardization and evaluation of vaccines. The European Medicines Agency (EMA) coordinates the European marketing authorizations.
“Of course, the most sensible thing to do early on after infection would be to treat with a good, strong antiviral drug to reduce the virus load in the body so that a severe course of the disease does not develop in the first place. And also for the infected person to be less infectious to others. It is always a question of the magnitude of the infection. If you can reduce the amount of virus in the body, one is not as infectious anymore. Later on, when the infection has developed, you will probably still give medication to fight the virus, but then you have to treat the organ damage that has formed as well. And this is unfortunately not only the lungs; the virus goes into the heart, it goes into the intestines, it can cause very small embolisms, i.e. blood clotting. All these consequences of the virus infection have to be treated in later stages or prevented. We are talking about entirely different drugs here.”
Published: November 2020
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